1. FIELD OF THE INVENTION
The present invention relates to a process of dyeing polyester fibers which have been modified so that they can be dyed with cationic dyes and more particularly the invention relates to a process of dyeing the modified polyester fibers black using a dyeing bath containing a specific combination of dyes.
2. DESCRIPTION OF THE PRIOR ART
Polyester fibers have been used widely as synthetic fibers having excellent properties for cloth but it has been difficult to dye such fibers a clear and deep color.
Of the various kinds of dyes, cationic dyes for polyacrylonitrile fibers give the most brilliant and deep color and various investigations have been made for modifying polyester fibers so that such fibers become cationic dye-dyeable and can be dyed brilliant and deep colors. As one result of these investigations, Japanese Pat. No. 10497/59discloses that polyester fibers can be modified for this purpose by copolymerizing them with sulfoisophthalic acid as an acid material.
However, when such modified polyester fibers are dyed with commercially available cationic dyes for polyacrylonitrile fibers, it is difficult to dye the fibers a deep black since modified polyester fibers are very poor in exhaustion for, in particular, black dyes. Furthermore, when yarn fabrics of blends of the basic dyeable polyester fibers with another kind or kinds of fibers are dyed, the fibers other than the polyester fibers are greatly stained.
That is, commercially available black dye compositions of cationic dyes for polyacrylonitrile fibers include the following combinations of dyes: ##SPC1## ##SPC2##
In the above formulae, X.sup.- represents an anion.
The above-described mixed dyes are very poor in exhaustion as stated above and hence do not result in a deep black color and in addition result in greatly staining fibers other than the basic dyeable polyester fibers when yarn fabrics of blends of these fibers are dyed with such mixed dyes.